The invention concerns an apparatus for the preparation of multilayer laminated plates, in particular, printed circuit boards for electrotechnical applications, wherein several webs of materials are brought together continuously by means of feeder installations, impregnated with a binder and subsequently pressed.
Various means are known for the preparation of multilayer laminated plates. For example, multilayer presses have found widespread use, into which webs of materials impregnated with binders are placed and pressed with a plunger. One difficulty of the process is that the applicable binders are solidified at room temperature and therefore must be mixed with a solvent in order to render the impregnation of the material webs possible. The solvent must then be removed by drying, making the process more cumbersome and labor intensive. Also, since the individual layers of each of the laminated plates to be produced must be manually stacked and placed in the multilayer press and removed after the pressing step, the capacity of such presses is low. Finally, the pressing time of laminating presses of this type is relatively long, as the point in time at which the binder passes into its solid state cannot be accurately determined and depends on a number of different factors, so that the impregnated webs of material must be left in the press until this point in time has safely passed.
Proposals for installations for the production of multilayer laminated plates have therefore already been presented, whereby the afore-described disadvantages, in particular, the low capacity of such devices were intended to be elminated. In DE-OS No. 26 13 081 for example, an apparatus of the afore-mentioned type is described, in which the individual webs are (i) brought together in an impregnating bath, (ii) moved with the aid of rolls several times into the bath and out of it, (iii) subsequently alternatingly flexed and pressed by means of calender rolls and, finally, (iv) finish pressed in a smoothing mill. The multilayer web may be heated or cooled both in the calender and the smoothing mill, wherein the rolls themselves may be heated or cooled.
This known apparatus does not, however, completely solve the problems encountered with multilayer presses. As the binder, for example a synthetic resin, requires a relatively long period of time for hardening, the transport velocity and the capacity of the apparatus cannot be increased arbitrarily. In order to maintain the resin in a liquid state in the impregnating bath, the pot-life must be made long, which in turn, results in a relatively long hardening time. Furthermore, the entire apparatus is rendered complex and expensive by the use of several rolling and squeezing systems. Finally, it cannot be warranted that the binder will attain its point of transformation from the liquid to the solid state exactly at the moment of its passage through the smoothing rolls. Since this transformation occurs abruptly in the case of many binders, premature or belated pressing leads to the discharge of excessively pressed plates or laminated plates with inadequate adhesion.
It is an object of the present invention to provide an apparatus of the afore-mentioned type whereby the above-cited disadvantages are avoided. The apparatus should, in particular, have a high capacity and should not be excessively costly.